The present invention relates to a device having a periodic wiring structure such as a semiconductor memory, CMOS image sensor, CCD sensor, liquid crystal panel or the like and a test device therefor.
Conventional test devices for a device having a periodic wiring structure for detecting formation failures due to particles (fine wastes) or the like in the process of fabricating a semiconductor device or liquid crystal panel include an optical-method test device using an optical sensor or the like to perform electronic image processing and an electrical-method test device, in which a current detecting tester is actually connected to a device to measure the currents flowing within the device and the obtained current values are used as judgement criteria. Also, apart from the aforementioned applications in the process of fabricating a semiconductor device or liquid crystal panel, there has been proposed a device for measuring currents flowing in the wiring pattern on a circuit board in which a magnetic force line sensor crossing the wiring pattern is disposed on a circuit board to detect magnetic force lines generated depending on the currents flowing in the wiring pattern so that the circuit is tested for normal operations (Japanese Patent Laid-Open Publication No. 6-5004)
Although the aforementioned optical-method test device can detect formation failures due to physical obstacles such as particles generated during a surface treatment process such as metal wiring or the like, there are problems in that it is extremely difficult to detect abnormalities within a device (for example, contact failure between wiring lines or the like) and a considerable amount of time is required for image processing resulting in a long measurement time.
On the other hand, the aforementioned electrical-method test device can electrically detect abnormalities within the device (contact failure or the like), but there is a problem in that a multiplicity of wiring lines need to be successively selected and measured resulting in a long measurement time. Also, physical foreign substances which are present between wiring lines cannot be detected as defects unless a short circuit exists. In some cases, the foreign substances are brought into contact with wiring lines after a test due to changes in their shape for some reason, thereby causing electrical failures. It is extremely difficult to detect such progressive failures.
Further, in the aforementioned device using the magnetic force line sensor to measure currents, the circuit must be fabricated in an electrically correct manner so as to generate correct magnetic force lines. Also, since the circuit must be formed in a correct physical shape so that the generated magnetic force lines correctly reach the sensor, the device has an advantage that physical and electrical fabrication abnormalities can be simultaneously observed. However, a multiplicity of magnetic force line sensors must be disposed in proportion to the large number of wiring lings in the device, such as bit lines, word lines and the like, in a semiconductor memory device. This causes the manufacturing cost to become very high. Also, a long test time is required to analyze the outputs from the multiplicity of sensors, which substantially increases the testing cost. Furthermore, only abnormal currents in portions where the sensors are disposed can be detected, which makes it difficult to respond to uncertain particle obstacles that can unpredictably occur anywhere in the device substrate.
Accordingly, an object of the present invention is to provide a device having a periodic wiring structure and a test device therefor at a low cost which can instantaneously perform an efficient judgment on whether the periodic wiring structure is fabricated in a physically and electrically correct manner and also respond to particle obstacles.
In order to achieve the above object, there is provided a device having a periodic wiring structure having a plurality of periodically disposed wiring lines, comprising
magnetic force line generating means for simultaneously connecting at least a plurality of wiring lines out of all the periodically disposed wiring lines to a current source to generate magnetic force lines in a periodic distribution pattern from the currents flowing in the plurality of wiring lines connected to the current source.
According to the device having a periodic wiring structure with the constitution described above, which makes use of wiring lines (bit lines, word lines and the like) disposed at regular periods on a semiconductor memory, CMOS image sensor, CCD sensor, liquid crystal panel or the like, all the periodically disposed wiring lines or at least a plurality thereof are simultaneously connected to a current source by the magnetic force line generating means so that currents are allowed to flow in the plurality of wiring lines connected to the current source. Consequently, magnetic force lines in a periodic distribution pattern depending on the physical shape of the wiring lines are generated from the wiring lines connected to the current source. The state of a fabricated device can be observed in a simple and highly accurate manner by observing this periodic distribution pattern of the magnetic force lines. For example, simple means such as a sheet attached with periodically disposed magnetic powder bodies overlapped on the device or the like can be used to instantaneously judge whether the periodicity of the wiring lines is correctly maintained.
In one embodiment of the present invention, the current source has a constant current function for keeping the currents, each flowing in each wiring line, generally constant.
According to the device having a periodic wiring structure of the above embodiment, damage to wiring lines or deterioration of reliability due to overcurrent upon connection with the current source can be prevented because the current source keeps each current flowing in each wiring line generally constant.
Also, there is provided a test device for testing a device having a periodic wiring structure comprising:
magnetic force line detecting means for sampling and detecting at predetermined intervals magnetic force lines in a periodic distribution pattern generated from the device having the periodic wiring structure;
moving means for moving the magnetic force line detecting means along the surface of the device on which the wiring lines are provided; and
pattern judging means for judging the periodic distribution pattern of the magnetic force lines detected by the magnetic force line detecting means.
According to the above test device for a device having a periodic wiring structure, in the device having a periodic wiring structure, at least a plurality of wiring lines of all the periodically disposed wiring lines are simultaneously connected to the current source by the magnetic force line generating means to generate magnetic force lines in a periodic distribution pattern by the currents flowing in the plurality of wiring lines connected to the current source. Then, the magnetic force lines having a periodic distribution pattern generated from the device having a periodic wiring structure are sampled and detected at predetermined intervals by the magnetic force line detecting means, which is moved by the moving means (actuator or the like) along the device surface. At this time, the period of the magnetic force line distribution pattern is made closer to the sampling interval so that a moire pattern (interference fringes) is generated by the interference between the period of the magnetic force line distribution pattern and the sampling period. By judging this moire pattern, whether the periodic wiring structure is fabricated in a physically and electrically correct manner can be efficiently determined in an instant. Also, irregularities in the distribution pattern of magnetic force lines depending on the physical shape of the wiring lines due to particle obstacles can be detected.
In one embodiment of the test device according to the present invention, the pattern judging means obtains a spatial frequency spectrum of the periodic distribution pattern of the magnetic force lines detected by the magnetic force line detecting means by Fourier transform and collates an obtained frequency spectrum with a spatial frequency spectrum of a reference distribution pattern.
According to the test device for a device having a periodic wiring structure of the above embodiment, the pattern judging means obtains a spatial frequency spectrum of the periodic distribution pattern of magnetic force lines detected by the magnetic force line detecting means by Fourier transform and collates the obtained spatial frequency spectrum with the reference spatial frequency spectrum of the distribution pattern of a conforming product. Thus, since the spatial frequency spectrum of a device to be measured can be instantaneously compared with the spatial frequency spectrum of a conforming product, whether the product is defective or not can be judged at a high speed.
In one embodiment of the test device, the magnetic force line detecting means is a one-dimensional magnetic force line detecting element array in which a plurality of magnetic force line detecting elements for detecting magnetic force lines generated from the device are arranged in one line; and
the moving means moves the one-dimensional magnetic force line detecting element array in the direction perpendicular to the direction of the array of the magnetic force line detecting elements along the surface of the device on which the wiring lines are provided.
According to the test device for a device having a periodic wiring structure of the above embodiment, the moving means moves the one-dimensional magnetic force line detecting element array in which a plurality of elements for detecting magnetic force lines generated from the device are arranged in one line in the direction perpendicular to the direction of the arrangement of the magnetic force line detecting elements along the surface of the device on which the wiring lines are provided to scan a two-dimensional space, which is the surface of the device to be measured. Thus, since the magnetic force lines can be sampled in a batch in the one-dimensional direction, which is the direction of the arrangement of the plurality of magnetic force line detecting elements, the magnetic force lines can be measured at a higher speed and a lower cost.
Also, there is provided a test device for testing a device having a periodic wiring structure comprising:
a two-dimensional magnetic force line detecting element array in which a plurality of magnetic force line detecting elements for detecting magnetic force lines in a periodic distribution pattern generated from the device having the periodic wiring structure; and
pattern judging means for judging the periodic distribution pattern of magnetic force lines detected by the two-dimensional magnetic force line detecting element array.
According to the above test device for a device having a periodic wiring structure, in the device having a periodic wiring structure, at least a plurality of wiring lines of all the periodically disposed wiring lines are simultaneously connected to a current source by the magnetic force line generating means to generate magnetic force lines in a periodic distribution pattern by the currents flowing in the plurality of wiring lines connected to the current source. Then, the magnetic force lines having a periodic distribution pattern generated from the device having a periodic wiring structure are sampled and detected by the two-dimensional magnetic force line detecting element array. At this time, the period of the magnetic force line distribution pattern is made closer to the sampling interval so that a moire pattern (interference fringes) is generated by the interference between the period of the magnetic force line distribution pattern and the sampling period. By judging this moire pattern, whether the periodic wiring structure is fabricated in a physically and electrically correct manner can be efficiently determined in an instant. Also, irregularities in the distribution pattern of magnetic force lines depending on the physical shape of the wiring lines due to particle obstacles can be detected. Further, since the magnetic force lines are sampled and detected in a batch in a two-dimensional space, which is the surface of the device to be measured by the two-dimensional magnetic force line detecting element array, no actuator or the like for moving the magnetic force line detecting elements or magnetic force line detecting element array is required, and thereby a higher-speed test device can be provided.